I am not a bonafide expert in this arena. Conceptually, an Orphan Drug status will help expedite the FDA approval review/approval process. In summary, the FDA has targeted Orphan drug disease areas as those where drugs are very much needed....as apparently there are not adequate drugs and/or therapies to treat these types of diseases.
So by targeting these unmet need; the path to commercialization should be expedited (as the FDA will and should be more willing to approve (consider worthy drugs to address this types of diseases).